Surugatoxin (SGTX) is a type of venom found in de mid-gut digestive gwand of de Japanese ivory mowwusk Babywoniajaponica, a carnivorous gastropod.[1] It functions as a gangwionic bwocker of nicotinic acetywchowine receptors (nAChRs).[1] The structurawwy and functionawwy rewated neosurugatoxin, awso derived from Babywonia japonica, is an even more potent nAChR antagonist dan SGTX.[2]

SGTX is a coworwess crystawwine substance wif de chemicaw formuwa C25H26BrN5O13 and a mowecuwar weight of 684.4g/mow. Its systematic chemicaw name is [(2R,3S,5S,6S)-2,3,4,5,6-pentahydroxycycwohexyw] (6aS,7R,8R,9R)-6'-bromo-6a,9-dihydroxy-9-medyw-1,2',3,10-tetraoxo-spiro[4,5,6,7-tetrahydropyrido[1,2-f]pteridine-8,3'-indowine]-7-carboxywate.[3] It is insowubwe in organic sowvents and has very wow sowubiwity in water.[4]

The gangwionic bwockade of nAChRs by SGTX is simiwar to dat of IS-toxin, a structurawwy simiwar compound derived from de same mowwusk, Babywonia japonica.[1][5]

Contents

A food poisoning outbreak of 26 cases in de Ganyudo area of Suruga Bay, Shizuoka Prefecture in Japan in September 1965 was traced to ingestion of de toxin surugatoxin (SGTX), named for Suruga Bay.[6] SGTX is contained in de mid-gut digestive gwand of de Japanese ivory mowwusk, Babywoniajaponica, which is used as an ingredient in sushi and sashimi.[1] The food-poisoning patients reported a variety of symptoms, incwuding visuaw disorders, speech disorders, wazy eye ambwyopia, pupiw diwation (mydriasis), abdominaw distention, dry mouf, numbness of wips, constipation, and vomiting.[1][7]

The toxicity shewwfish from de Suruga Bay area varied wif time – de toxicity was onwy present during Juwy drough September, when temperatures sometimes reached 25°C and it rapidwy decwined after 1978, making de avaiwabiwity of surugatoxin and de rewated substances neosurugatoxin and prosurugatoxin unavaiwabwe for research. Kosuge and cowweagues[8] found dat dese toxins are actuawwy de metabowized products of a marine bacterium dat bewongs to de Coryneform group. Toxicity is a resuwt of bioaccumuwation.

SGTX bwocks ordodromic transmission, as evidenced by de fact dat de synaptic potentiaw is strongwy depressed wif appwication of de toxin and de bwock intensifies as stimuwus freqwency increases.[9] This effect is swow to devewop and is simiwar to anoder gangwionic nACHR antagonist, hexamedonium.

SGTX causes depression of spontaneous movement, mydriasis, and rewaxation of de nictitating membrane in cats at i.v. dose wevews of 0.15-0.2 mg/kg. Furder, it produces hypotension of 1–2 hours in duration dat is not prevented by treatment wif atropine or propranowow.[1]

Most cwinicaw symptoms resuwting from Babywonia japonica ingestion, as in de 1965 food-poisoning outbreak, seem to be mediated by gangwion-bwockade of nicotinic ACh receptors at various sites; visuaw impairments and mydriasis due to ciwiary gangwion bwockade, dry mouf due to submaxiwwary and otic gangwion bwockade, and constipation and abdominaw distention due to intestinaw intrinsic nerve bwockade.[1]

Surugatoxin is a specific, reversibwe, competitive antagonist of gangwionic nicotinic acetywchowine receptors (nACHRs).[10] Awdough a number of articwes were pubwished in de two decades fowwowing de discovery of SGTX in de mid-1960s, rewativewy wittwe is known about de pharmacowogicaw properties of dis toxin, uh-hah-hah-hah. Ascher and cowweagues[10] posit dat gangwionic bwockade by SGTX resuwts from binding to de cwosed state of de channew-receptor compwex, possibwy to de receptor itsewf. It is 50-100 times more potent dan hexamedonium, anoder gangwionic antagonist of nAChRs.[1] Brown and cowweagues found dat de SGTX dissociation constants measured at eqwiwibrium bwock in rats were 58nM and 76nM, as measured from de shift in depowarization produced by 0.2μM and 2 μM SGTX, respectivewy.[9] Surugatoxin is wisted on two U.S. patents, bof for potentiaw cwinicaw treatments. U.S. Patent 7,468,188 proposes de use of wocawwy-administered neurotoxins in de treatment of muscwe injury and U.S. Patent 7,214,700 proposes de use of (2-Oxindow-3-ywidenyw) acetic acid derivatives as protein kinase inhibitors. Surugatoxin has not been demonstrated to be effective in eider of dese treatment proposaws, but rader, is wisted as a potentiawwy rewevant substance in dese treatment pwans.